<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
	*{ box-sizing:border-box; }
	#box{margin:50px;
		width:200px;
		height:100px;
		background: red;
		animation:aa 5s ease-in-out 2s 4 alternate;	}
	@keyframes aa{
			from{width:200px; }
			to{width:800px;}
		}

	</style>
</head>
<body>
	<div id="box">		
	</div>
</body>
</html>
